Stereospecific dimerization through π-conjugated systems of sulfur-bridged dinuclear cobalt(III)-platinum(II) complexes of 1,2-propanediamine

Reaction of Λ,Λ-[Ni{Co(aet)2(S-pn)}2]4+ (aet = 2-aminoethanethiolate pn = 1,2-propanediamine) in which Λ-cis(S)-[Co(aet)2(S-pn)]+ units act as bidentate metalloligands with [PtCl2(bpy)] (bpy = 2,2′-bipyridine) gave an optically active S-bridged dinuclear complex Λ-[Pt(bpy){Co(aet)2(S-pn)}](ClO4)3 (2) whose structure is enantiomeric to that previously reported for Δ-[Pt(bpy){Co(aet)2(S-pn)}] (ClO4)3 (1). A mixture of equimolar amounts of 1(ClO4)3 and 2(ClO4)3 in H2O crystallizes as Δ-[Pt(bpy){Co(aet)2(R-pn)}]0.5Λ-[Pt(bpy){Co(aet)2(S-pn)}]0.5(ClO4)3 · 2H2O (3(ClO4)3 · 2H2O) in which the enantiomeric complex cations 1 and 2 are included at a ratio of 1 : 1. The structure of 2 is consistent with that for 1 except for the absolute configuration at Co(III). The optically active cation in 2 exists as a monomer accompanied by no intermolecular π interactions with bpy moieties. However in crystals of 3(ClO4)3 · 2H2O the enantiomeric complex cations Δ-[Pt(bpy){Co(aet)2(R-pn)}]3+ and Λ-[Pt(bpy){Co(aet)2(S-pn)}]3+ in...